Histochemical and Chemical Studies of the Localization of Adrenergic and Cholinergic Nerves in Normal and Denervated Cat Hearts

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Abstract
The localization of adrenergic and cholinergic nerves in normal and denervated cat hearts was studied histochemically. The norepinephrine content of atria and ventricles was chemically determined by a spectrofluorometric method. In hearts denervated 9 to 42 days, little or no norepinephrine was detected. Histochemically, many catecholamine-containing fibers were present in the atria and ventricles of normal cats, whereas in denervated cats there were none in one and very few in four. There were many cholinergic nerves in the atria and a small to moderate number in the ventricles. The left atria of denervated hearts showed a marked reduction in cholinergic nerve fibers. It is concluded that cardiac denervation by mediastinal neural ablation is often incomplete. When norepinephrine is not detectable by chemical analysis, individual nerve fibers not sectioned can still be histochemically identified.